5 March 2003 PSF monitoring and in-focus wavefront control for NGST
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Abstract
A technique for measuring the low-order wavefront aberrations in segmented-mirror telescopes using in-focus point-spread functions -"PSF Monitoring" - has been developed for the Next Generation Space Telescope (NGST). PSF Monitoring will enable the continuous monitoring of the mirror segment alignment using the PSFs readily available in science data. An extension of PSF Monitoring - in-focus wavefront control, or the explicit determination and correction of wavefront errors from in-focus images - may allow for the nominal maintenance of the NGST mirror alignment without detracting from valuable science observing time. PSF Monitoring and in-focus wavefront control have been rigorously tested on the segmented aperture system of the NGST Wavefront Control Testbed (WCT). This paper presents the results of our experiments and simulations to characterize the capture range and accuracy on WCT, as well as a two-wavelength algorithm that has been used to extend the piston capture range. A real-time PSF Monitoring and control experiment on WCT will also be presented. Finally, we show preliminary simulation results of PSF Monitoring on the two candidate NGST systems.
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Catherine Mayumi Ohara, Catherine Mayumi Ohara, David C. Redding, David C. Redding, Fang Shi, Fang Shi, Joseph Jacob Green, Joseph Jacob Green, "PSF monitoring and in-focus wavefront control for NGST", Proc. SPIE 4850, IR Space Telescopes and Instruments, (5 March 2003); doi: 10.1117/12.461214; https://doi.org/10.1117/12.461214
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